The present invention relates to a process for enhancing the value of mixtures containing polychloropicolines and hexachlorobenzene.
Hexachlorobenzene is an undesirable contaminant that is generally produced as a by-product in high temperature picoline chlorination processes. The removal of this hexachlorobenzene contaminant from the polychloropyridine and polychloropicoline products obtained in such processes is critical to the usefulness of the products because of the toxicological and environmental properties of this contaminant. Polychloropyridines and polychloropicolines containing substantial amounts of hexachlorobenzene cannot be used directly or as intermediates.
Hexachlorobenzene can be reduced to low levels from mixtures with polychloropyridines and polychloropicolines having boiling points differing from that of hexachlorobenzene by about 40.degree. C. or greater by distillation. Such distillations are usually performed in high efficiency, multiplate stills under reduced pressure. Commercially feasible methods are not available, however, for removing hexachlorobenzene to acceptably low levels from mixtures with more closely boiling polychloropicolines and such mixtures are generally treated as waste. As a result, methods for removing hexachlorobenzene from mixtures with polychloropicolines and recovering usable polychloropyridines would be economically advantageous.